There are many types of lifting devices known in the prior art. For example, a pivoted lever (e.g. a pole supported by a rock) may be used to move or dislodge a heavy object. Other, more sophisticated lifting devices include pulley blocks, hand-chain hoists, and motor driven lifting systems such as cranes and elevators. Another type of lifting device is the jack. A jack is typically a portable, manually operated device for moving or lifting heavy loads or objects a short vertical distance. Jacks are frequently used, for example, to raise or lower one side of an automobile in order to facilitate the replacement of a flat tire.
There are many types of jacks well known in the art. Two types of jacks that require rotational actuation movement are a screw jack and a scissor jack--both have an input gear which must be rotated. Two types that use lever-like movement for actuation (that is, the up and down movement of a handle or lever) are a hydraulic jack and a rack-and-lever jack. Both types of jacks typically have some elements in common. These include a base plate or platform, which provides a ground support for the jack, a stand, which houses the inner movable components of the jack, a load bearing assembly, which supports and retains the load to be raised or lowered, and an actuator coupler, which receives the lever or handle by which the jack is operated.
Turning now to FIG. 1, a perspective view of a simplified screw jack, according to the prior art, is shown. A base plate 10 supports a stand 12. The stand 12 houses the internal components of the jack (not shown) which is actuated via an actuator coupler 14 (here, a square female connector). A handle 16, only partially shown in this Figure, engages with the actuator coupler 14. The handle 16 is rotated either clockwise or counter-clockwise to facilitate operation of the jack.
The internal components of the screw jack, which are not illustrated in further detail as such components are well known in the art, are not particularly relevant to the present invention. The handle 16 directly rotates a first gear, which has a center coupling assembly adapted to engage with a drive end of the handle. The first gear, in turn, rotates a gear assembly (according to a particular power transferring gear ratio as is well known in the art) which, in turn, rotates a first screw. That first screw then rotates a vertically oriented screw (which is typically integral with the load bearing assembly 18) which, in turn, moves axially with respect to the stand 12 (i.e. vertically up or down). Thus the load supported by the load bearing assembly 18 is either raised or lowered, as desired, depending upon the rotational direction of the handle 16. Because of the arrangement of the internal mechanism and the gear ratio, a single person, using the jack, is able to raise or lower a substantial load after numerous rotations of the handle.
Every manually operated jack requires some sort of actuating handle or lever to control operation thereof. Typically one end of the handle has a hand grip, and the other end has an actuator coupler adaptor that is shaped to engage with the actuator coupler provided on the jack so that a mating engagement between the actuator coupler adaptor of the handle and the actuator coupler of the jack is achieved to facilitate operation of the jack. As mentioned above, a screw jack might require a handle having a square male actuator coupler adaptor which mates with a similarly but oppositely shaped female actuator coupler 14.
A scissor jack, as well as some screw jacks, which typically have U-shaped actuator couplers, might require a "bent-shaft" adaptor (as discussed below in further detail). A prior art U-shaped actuator coupler is shown in FIG. 2.
As seen in FIG. 2, the U-shaped actuator coupler consists of a U-shaped bracket or actuator coupler 30 having a base plate 32 and two parallel side plates 34. Each side plate 34 has a circular void or aperture 36 formed therein near a center of the side plate. An actuator coupler shaft 38is connected to the base plate 32 on the side opposite the two side plates 34. The U-shaped actuator coupler shaft 38 is, in turn, permanently connected (e.g. threadedly engaged, welded, etc.) to the internal mechanism of the jack, for example, to a center of a gear.
To operate the U-shaped actuator coupler 30, a handle having a mating bent-shaft adaptor is utilized. Such a handle is diagrammatically shown in FIG. 3 (not to scale). A shaft 50 has opposed first and second ends. A first hand grip 52 is provided on a first end of the shaft 50. A U-shaped formation 54 is provided along an intermediate portion of the shaft 50 and a second hand grip 56 is disposed around the central area of the U-shaped formation 54. The second end of the shaft 50 is bent, forming a bent-shaft portion 58, i.e. the bent shaft adaptor, which is configured to engage with the U-shaped actuator coupler 30.
The diameter of the bent-shaft portion 58 should be slightly less than the diameter of the circular apertures 36 formed in the side plates 34 to facilitate ease of engagement. The bent-shaft portion 58 should have a length B (see FIG. 3) which is slightly longer than the width A of the U-shaped actuator (see FIG. 2) to prevent the bent-shaft portion 58 from becoming inadvertently disengaged from the U-shaped actuator coupler 30 while operating the jack.
During use, an operator inserts the bent-shaft adaptor 58 through one or both of the circular apertures 36. The operator then grasps the first hand grip 52 with one hand and the second hand grip 56 with the other. Thereafter, the operator then rotates the bent-shaft handle in a desired rotational direction which, in turn, rotates the U-shaped actuator coupler thereby raising or lowering the jack, as desired, depending upon the direction of rotation.
One major inconvenience associated with jacks requiring rotational actuation movement is that an operator generally has to turn the actuator coupler 14 a significant number of revolutions. This is because such jacks, by their very nature and advantage, convert energy inputted over a relatively long period of time (via the jack handle being rotated by an operator and the jack's internal gear mechanism) into a substantial upward raising or lowering force. Thus, for example, a driver changing a flat tire will have to rotate the jack handle for quite a long period of time (e.g. 20 second to a few minutes or so) before the automobile is sufficiently raised or lowered.
This problem is even more pronounced if multiple jacks are involved in a particular application. For example, to lift a camper on or off a truck bed or to level or stabilize a recreational vehicle, one jack is positioned adjacent each corner of the camper or recreational vehicle. The operator then sequentially operates each of the four jacks via appropriate handle movement until the camper or recreational vehicle is sufficiently elevated, leveled and/or stabilized. To ensure that the camper or recreational vehicle remains substantially level at all times, each jack is only raised or lowered a small distance at one time, e.g. only raised or lowered a fractionally distance of the total distance to be traveled. Thus, not only does the operator have to move the jack handle from jack to jack, but the total time spent involved in rotating the handle to raise or lower all the associated jacks can be several minutes or so.